1. Field of the Invention
The present invention relates to a rotating blade body which is mounted to a turbine part of a gas turbine, a steam turbine, a jet engine and the like or mounted to an air compressor of a gas turbine and a jet engine and rotates with a main shaft in an integrated manner.
2. Description of the Prior Art
Generally, in a turbine part of a gas turbine and the like and in an air compressor, a main shaft is installed inside a casing constructing an outer shape so as to rotate against the casing. Rotor discs are installed to this main shaft in a plurality of stages axially, and a plurality of rotating blades are extending from the outer circumference of each of the rotor discs in a radial pattern. These rotor discs and rotating blades constitute a rotating blade body, which rotates together with the main shaft in an integrated manner. Additionally, stationary vanes are installed to the casing along the main shaft so as to be arranged in a manner of alternating with the rotating blades.
In a case of a gas turbine, in such a turbine part constructed as described hereinabove, high temperature and high pressure combustion gas is supplied from a combustor as a working fluid, and by having this combustion gas flow through the rotating blades and the stationary vanes alternately, the main shaft is rotary driven together with the rotating blades, namely with a rotating blade body. Then, when a generator is connected to an edge of the main shaft, turning force of the main shaft is utilized as a source of electric power generation. On the contrary, when an injection port for exhaust of combustion gas is installed at an end of the turbine part, turning force of the main shaft is utilized as a jet engine. In a case of a steam turbine, by having high pressure steam flow through the rotating blades and the stationary vanes alternately as a working fluid, the main shaft is rotary driven, and turning force of the main shaft is utilized as a source of electric power generation of a generator.
On the other hand, in an air compressor of a gas turbine, a rotating blade body rotates together with a main shaft by rotation of the main shaft. By this, the air is inhaled from the outside as a working fluid and supplied to a combustor, being compressed by way of the rotating blades and the stationary vanes alternately. Here, compressed air being introduced into a combustor is burned with a fuel being supplied, resulting in high temperature and high pressure combustion gas, which is to be supplied to a turbine part of the above-mentioned gas turbine.
Here, a rotating blade body consists of rotor disc and rotating blades that are manufactured independently, being constructed in a manner that the rotating blades are assembled to the rotor disc. For example, as shown in FIG. 6, rotating blades 1 mainly have a blade root portion 10, a platform portion 11 and a blade portion 12, sequentially from the side of the center of the rotating shaft of the rotating blade body.
The blade root portion 10 is a portion which has a shape of cross section thereof viewed in the direction of the rotating shaft formed to be just like a Christmas tree and fits into an after-mentioned blade-inserted groove 20 in a rotor disc 2, functioning to support the whole of the rotating blade 1 against the rotor disc 2. The platform portion 11 is a portion serving as a pedestal which connects the blade root portion 10 to the blade portion 12, covering the outer circumference of the rotor disc 2. The blade portion 12 is a portion which has a transverse plane thereof shaped to be streamlined, extends, being gradually twisted while maintaining the streamline shape, and functions so as to have fluid such as a combustion gas, high pressure steam or air flow smoothly.
On the other hand, on the marginal part of the outer circumference of the rotor disc 2, blade-inserted grooves 20 being shaped to be approximately the same as the cross-sectional shape of the blade root portion 10 of the rotating blade 1 are formed along the rotating shaft at regular intervals in a circumferential direction. Into each of these blade-inserted grooves 20, the blade root portion 10 of the rotating blade 1 is inserted from the direction of the rotating shaft and engaged. In this way, each of the rotating blades 1 is assembled to the rotor disc 2, so as to obtain a rotating blade body in which a plurality of rotating blades 1 extend from the outer circumference of the rotor disc 2 in a radial pattern.
Especially, in a case of a rotating blade body which is to be mounted to a turbine part of a gas turbine and the like, because the blade portions 12 are exposed to high temperature atmosphere by high temperature working fluid, an ingenuity is exercised in order to restrain an excessive increase in temperature of the rotating blades 1 themselves being caused by the aforementioned exposure. (For example, see the Japanese Patent Application Laid-Open No. H07-305602.) To be more precise, the outer circumference surface of the rotor disc 2 and the portions from the platform portions 11 and 11 of the rotating blades 1 and 1 being in circumferential direction to the roots of the blade root portions 10 and 10 form circulation spaces 5 along the direction of the rotating shaft in order to have a cooling fluid (an air, for example) circulate therein. By having the cooling fluid circulate in these circulation spaces 5, heat exchange is exercised directly between the rotating blades 1 and the circulation spaces 5, which results in cooling of the rotating blades 1 themselves, thereby restraining the increase in temperature.
However, when excessive combustion gas leaks out into the circulation spaces 5 through the gaps between the adjacent platform portions 11 and 11, output to be obtained in the turbine part will be significantly deteriorated. Therefore, a sealing construction is provided so as to prevent excessive leakage of the combustion gas. To be more precise, as shown in FIG. 6, FIG. 7A and FIG. 7B, one of the end surfaces of the platforms 11 and 11 facing each other in circumferential direction with a space left between there has a sealing-pin-inserted groove 11a formed along the direction of the rotating shaft; wherein a sealing pin 3 being a column-shaped solid axle is inserted into the sealing-pin-inserted groove 11a. The sealing pin 3 is extending along the direction of the rotating shaft and is in contact with an end surface of the other platform portion 11, exercising sealing function to prevent the combustion gas from leaking out.
In addition, in the blade-inserted grooves 20 in the rotor disc 2, only the portions serving as the bottoms are widened largely toward the edges of the blade root portions 10 of the rotating blades 1, and the edges of the blade root portions 10 and the bottom portions of the blade-inserted grooves 20 form circulation spaces 6 along the direction of the rotating shaft in order to circulate a cooling fluid which is different from the above-mentioned cooling fluid. This construction is employed for a case where the rotating blades 1 are hollow rotating blades, in other words, for a case where flow passageways are formed inside the rotating blades 1 from the edges of the blade root portions 10 to the side surfaces and tips of the blade portions 12. The cooling fluid circulating in the circulation spaces 6 is introduced to the flow passageways inside the rotating blades 1 from the inlets which open at the edges of the blade root portions 10, exercises heat exchange with the rotating blades 1 while circulating through the flow passageways, and subsequently, is discharged through the outlets which open at the side surfaces and edges of the blade portions 12. The rotating blades 1 are cooled from the inside in the manner as described hereinabove. Incidentally, the cooling fluid being discharged from the side surfaces of the blade portions 12 becomes a film fluid which flows, covering the surfaces of the blade portions 12, and this film fluid provides a thermal insulation effect from the working fluid.
And now, the sealing pins 3 are expected to have a damping function, which is not known exactly but damps vibrations being caused to the rotating blades 1, in addition to the sealing function that prevents combustion gas from leaking out into the circulation spaces 5 being formed by the rotating blades 1 and 1 that are adjacent in circumferential direction. To put it plainly, because each of the rotating blades 1 is supported to the rotor disc 2 by having the blade root portion 10 thereof inserted into the blade-inserted groove 20 in the rotor disc 2 to be fit in, the platform portion 11 and the blade portion 12 will be in such a condition respectively as will vibrate in the circumferential direction with the blade root portion 10 serving as a supporting point independently while rotating together with the main shaft during operation. However, because the adjoining rotating blades 1 are bound by having the sealing pins 3 intervene at the platform portions 11 thereof, a damping force due to existence of the sealing pins 3 acts on the rotating blades 1, so that the vibrations come to be damped.
However, although the above-mentioned general sealing pins 3 of solid axle are expected to provide a damping effect, on the contrary, due to an increase in natural frequencies of the rotating blades 1 themselves, vibrations being caused to the rotating blades 1 during steady operation, resonance, and the like, adverse effects on restraining of the vibrations of the rotating blades 1 arose as a result. Therefore, accurate judgment could not be made.